Dielectric ceramic compositions

ABSTRACT

A dielectric ceramic composition consisting essentially of: 
     
         PbTi.sub.x (Mg.sub.1/3 Nb.sub.2/3).sub.y (Ni.sub.1/2 W.sub.1/2).sub.z 
    
      O 3   
     wherein x+y+z=1, which allows low-temperature sintering and has a high dielectric constant, a low dielectric loss and a high specific resistivity.

FIELD OF THE INVENTION AND RELATED ART STATEMENT

1. Field of the Invention

The present invention relates to dielectric ceramic compositions capable of sintering at low-temperature, exhibiting a high dielectric constant, low temperature coefficient of the dielectric constant and low dielectric loss, and being suitable for use in ceramic capacitors. 2. Description of the Related Art

As promising ceramic compositions for the above-mentioned purpose, those essentially consisting of BaTiO₃ have been widely used as substance of high dielectric constant. The dielectric constant of this substance has a relatively high temperature coefficient of the dielectric constant, while in general, a dielectric substance which exhibits a low temperature coefficient of the dielectric constant has a relatively low dielectric constant.

The temperature coefficient of a ceramic capacitor is established or defined by JIS (Japanese Industrial Standard) or EIA (U.S. Electronics Industries Association) Standard. For example, the temperature coefficient of a dielectric constant adaptable to YF rating of JIS, which is approximately equivalent to Y5 V rating of EIA Standard, means that the temperature coefficient varies within a range of +22 to -82% for operating range of -30° C. to 85° C. A dielectric material which exhibits a dielectric constant of 10,000, is adaptable to YF or Y5 V. However, BaTiO₃ system ceramics must be sintered at a very high temperature in the range of 1300° C. to 1400° C., so that where they are used as a dielectric substance of multilayer ceramic capacitors, expensive metals such as platinum or palladium which can stand such high sintering temperature must be used as internal electrodes of the capacitors, thereby obstructing cost reduction. Therefor there has still been a demand for dielectric ceramic materials which can be sintered at a temperature as low as below 1100° C. for enabling the use of relatively cheap metal such as silver-30% palladium for the internal electrodes.

U.S. Pat. No. 4,078,938 discloses binary system ceramic compositions of Pb(Fe_(2/3) Nb_(1/3))O₃ -Pb(Fe_(1/2) W_(1/2))O₃ which can be sintered at a temperature as low as below 1000° C., and which exhibit a high dielectric constant of 20,000. However, the resultant ceramics have a relatively low specific resistivity.

U.S. Pat. No. 4,265,668 discloses binary system ceramic composition PbTiO₃ -Pb(Mg_(1/3) Nb_(2/3))O₃, which exhibit a high dielectric constant of 20,000.

However, the ceramic compositions of this binary system must be sintered at a temperature range of 1100° C. to 1150° C.

U.S. Pat. No. 4,450,240 discloses ternary system ceramic compositions of PbTiO₃ -Pb(Ni_(1/3) Nb_(2/3))O₃ -Pb(Mg_(1/2) W_(1/2))O₃, which can be sintered at a temperature range of 900° C. to 1050° C. and exhibit a high electrical resistivity. However, the ceramics have a dielectric constant under 15,000.

SUMMARY AND OBJECT OF THE INVENTION

The object of the present invention is to provide a dielectric ceramic composition which can be sintered at a temperature as low as below 1100° C., and exhibits high dielectric constant and a high specific resistivity.

To attain the object, a ceramic composition of the present invention is a dielectric ceramic composition essentially comprising a substance represented by the formula.

    PbTi.sub.x (Mg.sub.1/3 Nb.sub.2/3).sub.y (Ni.sub.1/2 W.sub.1/2).sub.z O.sub.3

wherein x+y+z=1.00.

Other mode of the present invention contains MnO₂, Cr₂ O₃, CoO And MoO₃ as an additive.

Still other mode of the invention contains Pb(Mn_(1/3) Nb_(2/3))O₃.Pb(Mn_(1/2) Sb_(2/3))O₃ as an additive.

These novel composition of the present invention can be sintered at a temperature in the range from 900° C. to 1100° C., and have a high dielectric constant up to 8,000, and low temperature coefficient of the dielectric constant which meet the YF rating of JIS or Y5 V rating of EIA standard, and further it has a high specific resistivity.

BRIEF DESCRIPTION OF THE DRAWING

The accompanying drawing is a composition diagram of PbTiO₃ -Pb(Mg_(1/3) Nb_(2/3))O₃ -Pb(Ni_(1/2) W_(1/2))O₃ ternary system, wherein the polygon ABCDE shows a range of composition of the ceramic composition in accordance with the present invention.

DETAILED DESCRIPTION OF THE INVENTION

The composition herein may be prepared in accordance with various well-known ceramic procedures.

EXAMPLE 1

The starting materials, viz. lead oxide (PbO), titanium oxide (TiO₂), niobium oxide(Nb₂ O₅), magnesium oxide(MgO), nickel oxide(NiO), tungsten oxide(WO₃), all relatively pure grade, were initially mixed in a ball mill with distilled water and agate balls, for 17 hours. Thereafter the mixture was dried and then pressed into columns, and calcined at a temperature in the range of 750° C. to 880° C. for 2 hours in an aluminum crucibles. The substance thus obtained were wet ground in a ball mill, dried, mixed with polyvinyl alcohol as a binder solution, and then pressed into columns of about 13 mm in diameter and about 10 mm in length at a pressure of 700 Kg/cm². After buring out the binder at about 700° C., the pressed columns were put into a magnesia crucible and were sintered at a temperature in the range of 900° C. to 1100° C. for 2 hours. The sintered bodies were cut into disks of about 1 mm in thickness, and Cr-Au electrodes were attached on both surfaces of the disks by a method of vacuum evaporation.

Various properties of the ceramic disks thus obtained are shown in TABLE 1. The dielectric constant (ε) and the dielectric loss (tan δ) were measured at a frequency of 1 KHz and a voltage of 1 V at 20° C. The temperature coefficients of the dielectric constant were obtained by measuring the dielectric constants at temperatures in the range of -25° C. to 85° C. and then calculations are made with reference to the dielectric constant at 20° C.

The sintering temperature is selected as the temperature wherein the density of the sintering columns has maximum.

The specific resistivity is measured at 20° C. under application of a D.C. voltage of 1000 V.

From TABLE 1 it is obvious that the ceramic compositions within the polygon ABCDE in the ternary system composition diagram of the drawing provide a

                                      TABLE 1                                      __________________________________________________________________________                 Sintering  tan δ                                                                         Change of   Specific                               Composition temperature                                                                           ε                                                                          20° C.                                                                       ε (%)                                                                              resistivity                            No.                                                                               x  y  z  (°C.)                                                                          20° C.                                                                      (× 10.sup.-4)                                                                 (-25° C.)                                                                     (+85° C.)                                                                     (Ω · cm)                __________________________________________________________________________     1  0.025                                                                             0.950                                                                             0.025                                                                             1090   10780                                                                              400  -5.4  -34.0 6.0 × 10.sup.12                   2*                                                                               0.070                                                                             0.930                                                                             0.000                                                                             1150   21040                                                                              460  -54.6 -57.4 4.5 × 10.sup.11                  3  0.125                                                                             0.850                                                                             0.025                                                                             1090   17730                                                                              500  -66.0 -28.1 2.0 × 10.sup.13                   4*                                                                               0.350                                                                             0.600                                                                             0.050                                                                             1100    3200                                                                              640  -12.5 +128.2                                                                               8.0 × 10.sup.12                  5  0.375                                                                             0.450                                                                             0.175                                                                              980   10210                                                                              500  -74.3 -11.6 5.0 × 10.sup.12                  6  0.200                                                                             0.700                                                                             0.100                                                                             1000   21350                                                                              410  -60.0 -54.0 1.0 × 10.sup.13                  7  0.250                                                                             0.550                                                                             0.200                                                                              980   12110                                                                               90  -12.0 -55.0 8.0 × 10.sup.12                  8  0.200                                                                             0.550                                                                             0.250                                                                              900    9850                                                                               45  -8.1  -60.3 2.5 × 10.sup.12                   9*                                                                               0.100                                                                             0.600                                                                             0.300                                                                              900    4930                                                                               40  +121.2                                                                               -45.0 1.4 × 10.sup.12                  10 0.025                                                                             0.900                                                                             0.075                                                                             1030   11450                                                                               50  -13.3 -61.2 1.5 × 10.sup.13                  11*                                                                               0.000                                                                             0.930                                                                             0.070                                                                             1030    9660                                                                               50  -4.3  -89.6 1.2 × 10.sup.13                  12*                                                                               0.400                                                                             0.300                                                                             0.300                                                                              900    8760                                                                              102  -12.6 -45.3 1.0 × 10.sup.12                  __________________________________________________________________________      Note 1: Basic compositions PbTi.sub.x (Mg.sub.1/3 Nb.sub.2/3).sub.y            (Ni.sub.1/2 W.sub.1/2).sub.z O.sub.3                                           Note 2: Compositions of the Nos. with an asterisk (*) are outside the          scope of the present invention.   high dielectric constant (ε=         9850-21350), high specific resistivity, low dielectric loss (tan      δ≦500×10), low temperature coefficient of the      dielectric constant which is adaptable to YF ranges rating of JIS and Y5 V      rating of EIA Standard, and can be sintered below 1100° C., for      which the points A, B, C, D and E of FIG. 1 are represented by the values      of x, y and z as shown in TABLE 2.

The reasons for the limitations of values in TABLE 2 are as follows.

In case of the composition wherein proportions of z is smaller than 0.025 such as sample No. 2, the sintering temperature is higher than 1100a° C. Such compositions, which lie outside of line BC, DE and EA of the polygon ABCDE in the ternary system composition diagram as samples No. 4, 9 and 11, exhibit high temperature coefficients of dielectric constant. Such composition, which lies outside of line CD of the polygon ABCDE in the ternary system composition diagram, as sample No. 12 exhibits a dielectric constant which is lower than 9500.

EXAMPLE 2

The starting materials, viz. lead oxide(PbO), titanium oxide(TiO₂), niobium oxide(Nb₂ O₅), magnesium oxide(MgO), nickel oxide(NiO), tungsten oxide(WO₃), manganese oxide(MnO₂), cromium oxide(Cr₂ O₃), cobalt

                  TABLE 2                                                          ______________________________________                                         x                  y      z                                                    ______________________________________                                         A       0.025          0.950  0.025                                            B       0.125          0.850  0.025                                            C       0.375          0.450  0.175                                            D       0.200          0.550  0.250                                            E       0.025          0.900  0.075                                            ______________________________________                                    

oxide(CoO) and molybdenum oxide(MoO₃), all relatively pure grade, were initially mixed in a ball mill with distilled water and agate balls, for 17 hours. Thereafter the mixture was dried and then pressed into columns, and calcined at a temperature in the range 750° C. to 880° C. for 2 hours in an aluminum crucibles. The substance thus obtained were wet ground in a ball mill, dried, mixed with polyvinyl alcohol as a binder solution, and then pressed into columns of about 13 mm in diameter and about 10 mm in length at a pressure of 700 Kg/cm². After buring out the binder at about 700° C., the pressed columns were put into a magnesia crucible and were sintered at a temperature in the range of 900° C. to 1100° C. for 2 hours. The sintered bodies were cut into disks of about 1 mm in thickness, and Cr-Au electrodes were attached on both surfaces of the disks by a method of vacuum evaporation.

Various properties of the ceramic disks thus obtained are shown in TABLE 3. The dielectric constant and the dielectric loss were measured at a frequency of 1 KHz and a voltage of 1 V at 20° C. The temperature coefficients of the dielectric constants were obtained by measuring a dielectric constant at temperatures in the range of -25° C. to 85° C. and calculated with reference to the dielectric constant at 20° C.

The sintering temperature is selected as the

                                      TABLE 3                                      __________________________________________________________________________                        Sintering                 Specific                                      Additive                                                                              tempera- tan δ                                                                         Change of   resistivity                       Composition element                                                                               ture ε                                                                          20° C.                                                                       ε (%)                                                                              tivity                            No.                                                                               x  y  z  wt %   (°C.)                                                                        20° C.                                                                      (× 10.sup.-4)                                                                 (-25° C.)                                                                     (+85° C.)                                                                     (Ω · cm)           __________________________________________________________________________      1#                                                                               0.100                                                                             0.800                                                                             0.100                                                                             --  -- 1050 13930                                                                              310  +8.4  -54.1 1.2 × 10.sup.13              2 0.100                                                                             0.800                                                                             0.100                                                                             MnO.sub.2                                                                          0.05                                                                              1050 12230                                                                              122  +7.3  -48.3 1.2 × 10.sup.13              3 0.100                                                                             0.800                                                                             0.100                                                                             MnO.sub.2                                                                          0.20                                                                              1040 12100                                                                               63  +4.1  -43.0 1.4 × 10.sup.13              4*                                                                               0.100                                                                             0.800                                                                             0.100                                                                             MnO.sub.2                                                                          1.00                                                                              1010  5440                                                                              210  +5.1  -21.3 2.0 × 10.sup.12              5*                                                                               0.100                                                                             0.800                                                                             0.100                                                                             Cr.sub.2 O.sub.3                                                                   0.01                                                                              1040 13320                                                                              250  +8.1  -54.0 1.1 × 10.sup. 13             6 0.100                                                                             0.800                                                                             0.100                                                                             Cr.sub.2 O.sub.3                                                                   0.03                                                                              1030 13030                                                                              170  +5.1  -45.3 1.0 × 10.sup.13              7 0.100                                                                             0.800                                                                             0.100                                                                             Cr.sub.2 O.sub.3                                                                   0.15                                                                              1030 12420                                                                              102  +4.1  -45.4 7.5 × 10.sup.12              8*                                                                               0.100                                                                             0.800                                                                             0.100                                                                             Cr.sub.2 O.sub.3                                                                   0.70                                                                              1000 11450                                                                              340  +7.1  -21.9 2.5 × 10.sup.11              9*                                                                               0.100                                                                             0.800                                                                             0.100                                                                             CoO 0.02                                                                              1050 12980                                                                              280  +7.5  -49.3 1.0 × 10.sup.13             10 0.100                                                                             0.800                                                                             0.100                                                                             CoO 0.40                                                                              1010 11390                                                                              175  +4.3  -40.6 1.0 × 10.sup.13             11*                                                                               0.100                                                                             0.800                                                                             0.100                                                                             CoO 0.90                                                                              1000  5480                                                                              100  +12.5 -21.8 3.5 × 10.sup.11             12*                                                                               0.100                                                                             0.800                                                                             0.100                                                                             MoO.sub.3                                                                          0.01                                                                              1050 13640                                                                              300  +8.0  -54.1 1.1 × 10.sup.13             13 0.100                                                                             0.800                                                                             0.100                                                                             MoO.sub.3                                                                          0.40                                                                              1000 10960                                                                              180  +12.5 -43.7 8.5 × 10.sup.12             14*                                                                               0.100                                                                             0.800                                                                             0.100                                                                             MoO.sub.3                                                                          0.90                                                                              960   6490                                                                              250  +13.2 -31.7 8.0 × 10.sup.11             15 0.100                                                                             0.800                                                                             0.100                                                                             MnO.sub.2                                                                          0.10                                                                       CoO 0.05                                                                              1030 13340                                                                              100  +6.3  - 51.0                                                                               1.0 × 10.sup.13             16#                                                                               0.200                                                                             0.700                                                                             0.100                                                                             --  -- 1000 21350                                                                              410  -6.3  -54.0 1.0 × 10.sup.13             17*                                                                               0.200                                                                             0.700                                                                             0.100                                                                             MnO.sub.2                                                                          0.01                                                                              1000 21000                                                                              400  -6.2  -53.3 1.1 × 10.sup.13             18 0.200                                                                             0.700                                                                             0.100                                                                             MnO.sub.2                                                                          0.03                                                                              1000 20000                                                                              200  -6.0  -51.4 1.5 × 10.sup.13             19 0.200                                                                             0.700                                                                             0.100                                                                             MnO.sub.2                                                                          0.10                                                                              1000 19050                                                                              145  -0.4  -49.3 1.2 × 10.sup.13             20 0.200                                                                             0.700                                                                             0.100                                                                             MnO.sub.2                                                                          0.60                                                                              1000  8430                                                                               73  +1.5  -39.3 5.0 × 10.sup.12             21*                                                                               0.200                                                                             0.700                                                                             0.100                                                                             MnO.sub.2                                                                          1.00                                                                              980   5430                                                                              150  +7.8  -21.3 8.0 × 10.sup.11             22*                                                                               0.200                                                                             0.700                                                                             0.100                                                                             Cr.sub.2 O.sub.3                                                                   0.02                                                                              1000 20640                                                                              315  -5.3  -51.3 1.4 × 10.sup.13             23 0.200                                                                             0.700                                                                             0.100                                                                             Cr.sub.2 O.sub.3                                                                   0.30                                                                              950  14350                                                                              183  +9.3  -41.7 1.4 × 10.sup.13             24*                                                                               0.200                                                                             0.700                                                                             0.100                                                                             Cr.sub.2 O.sub.3                                                                   0.70                                                                              900  11430                                                                              235  +15.3 -30.8 7.0 × 10.sup.11             25*                                                                               0.200                                                                             0.700                                                                             0.100                                                                             CoO 0.01                                                                              1000 21430                                                                              315  -8.3  - 53.2                                                                               1.1 × 10.sup.13             26 0.200                                                                             0.700                                                                             0.100                                                                             CoO 0.25                                                                              980  20180                                                                              175  -5.4  -51.3 1.0 × 10.sup.13             27*                                                                               0.200                                                                             0.700                                                                             0.100                                                                             CoO 0.80                                                                              960  18930                                                                              220  -4.3  -50.6 3.0 × 10.sup.11             28*                                                                               0.200                                                                             0.700                                                                             0.100                                                                             MoO.sub.3                                                                          0.01                                                                              980  20740                                                                              325  -6.0  -53.1 8.5 × 10.sup.13             29 0.200                                                                             0.700                                                                             0.100                                                                             MoO.sub.3                                                                          0.40                                                                              950  16340                                                                              163  +3.1  -50.4 1.1 × 10.sup.12             30*                                                                               0.200                                                                             0.700                                                                             0.100                                                                             MoO.sub.3                                                                          1.00                                                                              910  13320                                                                              230  +5.1  -48.3 4.0 × 10.sup.11             31#                                                                               0.250                                                                             0.550                                                                             0.200                                                                             --  -- 980  12110                                                                               90  +4.4  -55.0 8.0 × 10.sup.12             32 0.250                                                                             0.550                                                                             0.200                                                                             MnO.sub.2                                                                          0.08                                                                              970  10940                                                                               32  +3.2  -48.3 8.5 × 10.sup.12             33 0.250                                                                             0.550                                                                             0.200                                                                             MnO.sub.2                                                                          0.40                                                                              950   8460                                                                               21  +0.3  -40.3 8.0 × 10.sup.11             34*                                                                               0.250                                                                             0.550                                                                             0.200                                                                             MnO.sub.2                                                                          0.80                                                                              940   5540                                                                               83  -0.9  -31.3 1.0 × 10.sup.11             35*                                                                               0.250                                                                             0.550                                                                             0.200                                                                             Cr.sub.2 O.sub.3                                                                   0.01                                                                              980  12330                                                                               87  +4.4  -55.3 8.0 × 10.sup.12             36 0.250                                                                             0.550                                                                             0.200                                                                             Cr.sub.2 O.sub.3                                                                   0.03                                                                              980  12120                                                                               74  +4.0  -51.3 1.0 × 10.sup.13             37 0.250                                                                             0.550                                                                             0.200                                                                             Cr.sub.2 O.sub.3                                                                   0.15                                                                              970  10770                                                                               40  +3.1  -43.3 1.3 × 10.sup.13             38 0.250                                                                             0.550                                                                             0.200                                                                             Cr.sub.2 O.sub.3                                                                   0.50                                                                              950   8960                                                                               85  +1.0  -38.8 4.5 × 10.sup.12             39*                                                                               0.250                                                                             0.550                                                                             0.200                                                                             Cr.sub.2 O.sub.3                                                                   1.00                                                                              930   5140                                                                              250  -3.5  -31.5 2.0 × 10.sup.11             40 0.250                                                                             0.550                                                                             0.200                                                                             CoO 0.30                                                                              960  11540                                                                              174  -3.1  -42.3 8.0 × 10.sup.12             41 0.250                                                                             0.550                                                                             0.200                                                                             CoO 0.50                                                                              960  10430                                                                              184  -6.3  -38.4 9.0 × 10.sup.11             42*                                                                               0.250                                                                             0.550                                                                             0.200                                                                             CoO 0.80                                                                              970   9440                                                                              230  -7.4  -36.5 1.5 × 10.sup.10             43*                                                                               0.250                                                                             0.550                                                                             0.200                                                                             MoO.sub.3                                                                          0.02                                                                              980  11340                                                                              210  +3.1  -53.2 8.5 × 10.sup.12             44 0.250                                                                             0.550                                                                             0.200                                                                             MoO.sub.3                                                                          0.15                                                                              960  10420                                                                              152  +7.3  -48.1 1.2 × 10.sup.12             45*                                                                               0.250                                                                             0.550                                                                             0.200                                                                             MoO.sub.3                                                                          0.80                                                                              960   5110                                                                              135  +4.3  -31.2 7.0 × 10.sup.11             __________________________________________________________________________      Note 1: Basic compositions PbTi.sub.x (Mg.sub.1/3 Nb.sub.2/3).sub.y            (Ni.sub.1/2 W.sub.1/2).sub.z O.sub.3                                           Note 2: Compositions of the Nos. with asterisk (*) are outside the scope       of the present invention, with sharp (#) are included in the claim 1.    

temperature wherein the density of the sintering columns has maximum.

The specific resistivity is measured at 20° C. under application of a D.C. voltage of 1000 V.

From TABLE 3 it is obvious that the ceramic compositions within the polygon ABCDE in the ternary system composition diagram of the drawing and containing at least one element selected from the group consisting of Mn, Cr, Co and Mo in an amount in total equivalent 0.03 to 0.06 weight % of respective oxides (MnO₂, Cr₂ O₃, CoO and MoO₃) exhibit low dielectric loss at the room temperature as compared with that of composition with no addition and exhibit still high dielectric constant even with low sintering temperature.

The reasons for the limitations in TABLE 3 are as follows.

If content of MoO₂, Cr₂ O₃, CoO and MoO₃ in total is smaller than 0.03 weight %, the dielectric loss at the room temperature is not improved. When the content in total is larger than 0.60 weight %, the dielectric loss becomes larger and specific resistivity becomes smaller.

EXAMPLE 3

The starting materials, viz. lead oxide(PbO), titanium oxide(TiO₂), niobium oxide(Nb₂ O₅), magnesium oxide(MgO), nickel oxide(NiO), tungsten oxide(WO₃), manganese oxide(MnO₂) and antimony oxide(Sb₂ O₅), all relatively pure grade, were initially mixed in a ball mill with distilled water and agate balls, for 17 hours. Thereafter the mixture was dried and then pressed into columns, and calcined at a temperature in the range 750° C. to 880a° C. for 2 hours in an aluminum crucibles. The substance thus obtained were wet ground in a ball mill, dried, mixed with polyvinyl alcohol as a binder solution, and then pressed into columns of about 13 mm in diameter and about 10 mm in length at a pressure of 700 Kg/cm². After buring out the binder at about 700° C., the pressed columns were put into a magnesia crucible and were sintered at a temperature in the range of 900° C. ato 1100° C. for 2 hours. The sintered bodies were cut into disks of about 1 mm in thickness, and Cr-Au electrodes were attached on both surfaces of the disks by a method of vacuum evaporation.

Various properties of the ceramic disks thus obtained are shown in TABLE 4. The dielectric constant and the dielectric loss were measured at a frequency of 1 KHz and a voltage of 1 V at 20° C. The temperature coefficients of the dielectric constants were obtained by measuring a dielectric constant at temperatures in the range of -25° C. to 85° C. and calculated with reference to the dielectric constant at 20° C.

                                      TABLE 4                                      __________________________________________________________________________                        Sintering                 Specific                                      Additive                                                                              tempera- tan δ                                                                         Change of   resistivity                       Composition element                                                                               ture ε                                                                          20° C.                                                                       ε (%)                                                                              tivity                            No.                                                                               x  y  z  wt %   (°C.)                                                                        20° C.                                                                      (× 10.sup.-4)                                                                 (-25° C.)                                                                     (+85° C.)                                                                     (Ω · cm)           __________________________________________________________________________      1#                                                                               0.100                                                                             0.800                                                                             0.100                                                                             --  -- 1050 13930                                                                              310  +8.4  -54.1 1.2 × 10.sup.13              2*                                                                               0.100                                                                             0.800                                                                             0.100                                                                             MnNb                                                                               0.20                                                                              1040 13010                                                                              220  +3.1  -52.3 1.0 × 10.sup.13              3 0.100                                                                             0.800                                                                             0.100                                                                             MnNb                                                                               0.80                                                                              1020 12150                                                                              107  +2.1  -50.1 8.0 × 10.sup.12              4 0.100                                                                             0.800                                                                             0.100                                                                             MnNb                                                                               2.00                                                                              1000 10840                                                                              102  -2.1  -48.1 8.5 × 10.sup.11              5*                                                                               0.100                                                                             0.800                                                                             0.100                                                                             MnNb                                                                               3.00                                                                              1000  9410                                                                              215  -2.1  -38.2 2.5 × 10.sup.11              6*                                                                               0.100                                                                             0.800                                                                             0.100                                                                             MnW 0.10                                                                              1040 13390                                                                              280  +7.1  -53.2 1.1 × 10.sup.13              7 0.100                                                                             0.800                                                                             0.100                                                                             MnW 0.50                                                                              1030 12840                                                                              147  +5.1  -50.4 8.0 × 10.sup.12              8 0.100                                                                             0.800                                                                             0.100                                                                             MnW 1.00                                                                              1000 10430                                                                               78  +2.1  -46.3 8.0 × 10.sup.12              9 0.100                                                                             0.800                                                                             0.100                                                                             MnW 2.50                                                                               960  6440                                                                              109  -3.5  -38.4 2.5 × 10.sup.12             10*                                                                               0.100                                                                             0.800                                                                             0.100                                                                             MnW 4.00                                                                               940  3180                                                                              215  -5.3  -30.6 7.5 × 10.sup.11             11*                                                                               0.100                                                                             0.800                                                                             0.100                                                                             MnSb                                                                               0.20                                                                              1040 13380                                                                              254  +7.1  -53.1 1.4 × 10.sup.13             12 0.100                                                                             0.800                                                                             0.100                                                                             MnSb                                                                               0.50                                                                              1040 12860                                                                              200  +4.3  -50.4 1.2 × 10.sup.13             13 0.100                                                                             0.800                                                                             0.100                                                                             MnSb                                                                               1.00                                                                              1030 11430                                                                               63  +1.3  -43.7 1.2 × 10.sup.12             14*                                                                               0.100                                                                             0.800                                                                             0.100                                                                             MnSb                                                                               3.00                                                                              1000  7420                                                                              212  -3.4  -39.8 5.0 × 10.sup.11             15 0.100                                                                             0.800                                                                             0.100                                                                             MnNb                                                                               1.00                                                                       MnW 0.50                                                                              1000 10840                                                                              174  -5.3  -48.3 1.2 × 10.sup.13             16#                                                                               0.200                                                                             0.700                                                                             0.100                                                                             --  -- 1000 21350                                                                              410  -6.3  -54.0 1.0 × 10.sup.13             17*                                                                               0.200                                                                             0.700                                                                             0.100                                                                             MnNb                                                                               0.30                                                                              1000 20140                                                                              280  -5.1  -53.1 1.2 × 10.sup.13             18 0.200                                                                             0.700                                                                             0.100                                                                             MnNb                                                                               0.50                                                                              1000 18430                                                                              172  -3.5  -50.6 1.0 × 10.sup.13             19 0.200                                                                             0.700                                                                             0.100                                                                             MnNb                                                                               1.30                                                                              1000 16430                                                                               74  +0.8  -48.2 8.0 × 10.sup.12             20 0.200                                                                             0.700                                                                             0.100                                                                             MnNb                                                                               2.50                                                                              1000 11130                                                                              168  +4.3  -39.2 6.0 × 10.sup.12             21*                                                                               0.200                                                                             0.700                                                                             0.100                                                                             MnNb                                                                               5.00                                                                               980  6990                                                                              254  +5.3  -36.4 1.0 × 10.sup.11             22*                                                                               0.200                                                                             0.700                                                                             0.100                                                                             MnW 0.10                                                                              1000 20410                                                                              313  -3.1  -50.1 1.0 × 10.sup.13             23 0.200                                                                             0.700                                                                             0.100                                                                             MnW 1.00                                                                               990 16890                                                                              174  -3.1  -50.1 8.0 × 10.sup.12             24 0.200                                                                             0.700                                                                             0.100                                                                             MnW 2.00                                                                               980 13380                                                                              184  +0.6  -43.2 5.0 × 10.sup.12             25*                                                                               0.200                                                                             0.700                                                                             0.100                                                                             MnW 5.00                                                                               940  8190                                                                              205  +3.2  -39.3 2.0 × 10.sup.11             26*                                                                               0.200                                                                             0.700                                                                             0.100                                                                             MnSb                                                                               0.10                                                                              1000 20030                                                                              305  -5.1  -53.1 1.5 × 10.sup.13             27 0.200                                                                             0.700                                                                             0.100                                                                             MnSb                                                                               0.50                                                                              1000 18630                                                                              200  -3.5  -51.2 1.5 × 10.sup.13             28 0.200                                                                             0.700                                                                             0.100                                                                             MnSb                                                                               1.00                                                                              1000 13340                                                                              106  +0.6  -43.9 1.0 × 10.sup.13             29 0.200                                                                             0.700                                                                             0.100                                                                             MnSb                                                                               2.50                                                                              1000 10140                                                                              184  +4.3  -39.3 4.0 × 10.sup.12             30*                                                                               0.200                                                                             0.700                                                                             0.100                                                                             MnSb                                                                               5.00                                                                               980  8430                                                                              213  +4.9  -39.4 1.0 × 10.sup.11             31#                                                                               0.250                                                                             0.550                                                                             0.200                                                                             --  --  980 12110                                                                               90  +4.4  -55.0 8.0 × 10.sup.12             32*                                                                               0.250                                                                             0.550                                                                             0.200                                                                             MnNb                                                                               0.30                                                                               980 11980                                                                               85  +3.1  -51.3 9.0 × 10.sup.12             33 0.250                                                                             0.550                                                                             0.200                                                                             MnNb                                                                               0.50                                                                               980 10830                                                                               35  +2.1  -49.3 8.0 × 10.sup.12             34 0.250                                                                             0.550                                                                             0.200                                                                             MnNb                                                                               1.00                                                                               980 10400                                                                               65  +0.3  -45.3 7.0 × 10.sup.12             35 0.250                                                                             0.550                                                                             0.200                                                                             MnNb                                                                               2.50                                                                               980  9125                                                                              168  +5.4  -39.8 5.0 × 10.sup.12             36*                                                                               0.250                                                                             0.550                                                                             0.200                                                                             MnNb                                                                               5.00                                                                               960  6050                                                                              256  +6.9  -37.4 1.0 × 10.sup.11             37*                                                                               0.250                                                                             0.550                                                                             0.200                                                                             MnW 0.30                                                                               980 11480                                                                               84  +3.3  -53.9 1.0 × 10.sup.13             38 0.250                                                                             0.550                                                                             0.200                                                                             MnW 1.50                                                                               960 10350                                                                               45  +1.2  -49.8 7.5 × 10.sup.12             39*                                                                               0.250                                                                             0.550                                                                             0.200                                                                             MnW 3.00                                                                               960  9420                                                                              212  -4.1  -36.3 4.5 × 10.sup.12             40*                                                                               0.250                                                                             0.550                                                                             0.200                                                                             MnSb                                                                               0.30                                                                               980 11490                                                                               90  +4.3  -52.0 9.0 × 10.sup.12             41 0.250                                                                             0.550                                                                             0.200                                                                             MnSb                                                                               1.00                                                                               980 10640                                                                              122  +4.1  -50.6 9.0 × 10.sup.12             42 0.250                                                                             0.550                                                                             0.200                                                                             MnSb                                                                               2.00                                                                               980  7130                                                                              178  +2.1  -46.3 7.5 × 10.sup.12             43*                                                                               0.250                                                                             0.550                                                                             0.200                                                                             MnSb                                                                               5.00                                                                               980  4130                                                                              105  +4.0  -50.1 5.0 × 10.sup.11             44 0.250                                                                             0.550                                                                             0.200                                                                             MnNb                                                                               0.50                                                                       MnW 0.50                                                                               980 11430                                                                              105  +4.0  -50.1 7.0 × 10.sup.12             45 0.250                                                                             0.550                                                                             0.200                                                                             MnNb                                                                               0.50                                                                       MnSb                                                                               1.00                                                                               980 11580                                                                              132  +1.4  -42.3 5.0 × 10.sup.12             __________________________________________________________________________      Note 1: Basic compositions PbTi.sub.x (Mg.sub.1/3 Nb.sub.2/3).sub.y            (Ni.sub. 1/2 W.sub.1/2).sub.z O.sub.3                                          Note 2: Compositions of the Nos. with asterisk (*) are outside the scope       of the present invention with sharp (#) are included in the claim 1.           Note 3: Additive elements MnNb means Pb(Mn.sub.1/3 Nb.sub.2/3)O.sub.3, Mn      means Pb(Mn.sub.1/2 W.sub.1/2)O.sub.3 and MnSb means Pb(Mn.sub.1/3             Sb.sub.2/3)O.sub.3.                                                      

The sintering temperature is selected as the temperature wherein the density of the sintering columns has maximum.

The specific resistivity is measured at 20° C. under application a D.C. voltage of 1000 V.

From TABLE 4 it is obvious that the ceramic compositions within the polygon ABCDE in the ternary system composition diagram of the drawing and containing at least one element selected from the group consisting of Pb(Mn_(1/3) Nb_(2/3))O₃, Pb(Mn_(1/2) W_(1/2))O₃ and Pb(Mn_(1/3) Sb_(2/3))O₃ in an amount in total quantity equivalent 0.50 to 2.50 weight % exhibit low dielectric loss at the room temperature as compared with that of composition with no addition and exhibit still high dielectric constant along with low sintering temperature.

The reasons for the limitations in TABLE 4 are as follows.

If contents of Pb(Mn_(1/3) Nb_(2/3))O₃, Pb(Mn_(1/2) W_(1/2)) and Pb(Mn_(1/3) Sb_(2/3))O₃ in total is smaller than 0.50 weight %, the dielectric loss at the room temperature is not improved. When the content in total is larger than 2.5 weight %, the dielectric loss becomes larger and specific resistivity becomes smaller.

As apparent from these Examples 1 to 4, the ternary ceramic compositions of the present invention have low sintering temperature below 1100° C., so that relatively cheap metal or alloy such as silver-30% palladium can be employed as internal electrodes of multilayer ceramic capacitors, and the durability of furnace used for sintering use may be extended and electric power for sintering may be lowered. Moreover, the ceramic compositions according to the present invention exhibit high dielectric constant together with high specific resistivity, low temperature coefficient of the dielectric constant and low dielectric loss. Therefor, the ceramic composition in accordance with the present invention are suitable for use in ceramic capacitors.

It will be evident that the starting materials to be used in the present invention are not limited to those used in the above-mentioned examples. Other oxide or compounds which are easily decomposed at elevated temperature may be used in place of the starting materials of the above examples. 

What is claimed is:
 1. A ceramic compositions comprising a substance represented by the formula

    PbTi.sub.x (Mg.sub.1/3 Nb.sub.2/3).sub.y (Ni.sub.1/2 W.sub.1/2).sub.z O.sub.3

wherein x+y+z=1 and the values of x,y and z fall within the ranges represented by the polygon ABCDE in the accompanying composition diagram of PbTiO₃ -Pb(Mg_(1/3) Nb_(2/3))O₃ -Pb(Ni_(1/2) W_(1/2))O₃ ternary system.
 2. A ceramic composition comprising a substance represented by the formula

    PbTi.sub.x (Mg.sub.1/3 Nb.sub.2/3).sub.y (Ni.sub.1/2 W.sub.1/2).sub.z O.sub.3

wherein x+y+z=1 and the values of x, y and z fall within the ranges represented by the polygon ABCDE in the accompanying composition diagram of PbTiO₃ -Pb(Mg_(1/3) Nb_(2/3))O₃ -Pb(Ni_(1/2) W_(1/2))O₃ ternary system and at least one element selected from the group consisting of Mn, Cr, Co and Mo in an amount in total equivalent to from 0.03 to 0.60 weight percent of respective oxides MnO₂, Cr₂ O₃, CoO and MoO₃.
 3. A ceramic composition comprising a substance represented by the formula

    PbTi.sub.x (Mg.sub.1/3 Nb.sub.2/3).sub.y (Ni.sub.1/2 W.sub.1/2).sub.z O.sub.3

wherein x+y+z=1 and the values of x, y and z fall within the ranges represented by the polygon ABCDE in the accompanying composition diagram of PbTiO₃ -Pb(Mg_(1/3) Nb_(2/3))O₃ -Pb(Ni_(1/2) W_(1/2))O₃ ternary system and at least one element selected from the group consisting of Pb(Mn_(1/3) Nb_(2/3))O₃, Pb(Mn_(1/2) W_(1/2))O₃ and Pb(Mn_(1/3) Sb_(2/3))O₃ in an amount in total equivalent to from 0.50 to 2.50 weight percent. 